What is the "standard 3-rig setup"?
You are essentially correct.

The standard 3 rig setup is as follows:


IK control chain
FK control chain
Deform chain


With the deform chain constrained to both control chains with copy rotation etc, and a driver setup to control the influence of those constraints so only one control chain influences the deform chain at a time.

In blender this is usually done all within one armature, rather than as separate objects, although it could be done separately if you wanted to.

The easiest example to find is the one that comes bundled with blender itself -  the generated Rigify rig uses this setup for arms and legs (Although it has an extra chain prefixed with ORG between the control chains and the deform chain (bones prefixed with DEF), for other reasons).